München 2004 – scientific programme

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MO: Molekülphysik

MO 15: Femtosekundenspektroskopie: Photoelektronen + Isomerisierung

MO 15.7: Talk

Tuesday, March 23, 2004, 18:00–18:15, HS 315

Impact of a strong Push-Pull Substitution on the Femtosecond Isomerisation of Azobenzene — •Bernhard Schmidt, Constanze Sobotta, Stefan Malkmus, Stefan Laimgruber, Markus Braun, Wolfgang Zinth, and Peter Gilch — Sektion Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538 München, Germany

Due to its prototypical character the isomerisation of azobenzenes has been subject to many femtosecond studies dealing with the parent compound. A push-pull substitution reduces the thermal isomerisation times. Here we report on femtosecond fluorescence and absorption experiments on the photodynamics of the push-pull compound 4−nitro−4^′(dimethylamino)−azobenzene (NA). Immediately after excitation, the emission of NA mirrors the absorption spectrum. This emission decays within 100 fs and is followed by a broad red-shifted emission decaying in 1 ps. This behaviour recurs in the absorption data which in addition yield information on the ground state recovery and cooling processes. The recovery dynamics suggest that the 100 fs process does not lead to a re-population of the ground state. Though qualitively similiar to azobenzene, in NA all processes are accelerated.